Interhemispheric Interaction and the Development of Speech and Language Skills in Preschool Children

Abstract

Interhemispheric interaction is frequently invoked to explain the development of speech and language in preschool children, yet the term encompasses distinct neural constructs, including lateralization, functional connectivity, effective connectivity, and white-matter organization. This critical narrative review examined what current evidence supports regarding the developmental, clinical, and practical significance of these constructs. Thirty full-text publications were synthesized across four domains: conceptual and methodological foundations, typical preschool development, developmental language and speech disorders, and intervention evidence with related neuromyths. Several developmental studies are compatible with early bilateral participation and emerging left-hemisphere specialization, but the timing and interpretation of these patterns vary with task, age, analytic method, and the distinction between activation and connectivity. Clinical findings remain heterogeneous, and structural white-matter differences do not establish a functional mechanism or a diagnostic threshold. Within the present corpus, the most direct intervention evidence concerns targeted speech-language treatment; the reviewed literature does not establish hemispheric balancing or generic neural synchronization as a speech treatment mechanism. Interhemispheric interaction is therefore best understood as one component of a dynamically maturing distributed language network. Current evidence does not support treating it as an independent causal determinant, validated diagnostic biomarker, or stand-alone therapeutic target for preschool speech. Longitudinal studies linking neural measures to standardized speech-language outcomes are needed.